The Mediterranean diet has been linked to a longer and healthier life, but the reason why is not completely clear yet. It is likely to be due to a multitude of factors, such as plenty of fruit and vegetables, garlic, fish, a more outdoor lifestyle…Olive oil is a key component, and the latest publication from the Predimed study shows that the extra-virgin variety is the most beneficial, suggesting that the effects are mainly due to its phytochemicals.
We assumed for many years that the benefits of olive oil are due to its high content of mono-unsaturated fatty acids. However, many foods in a typical Western diet contain plenty of mono-unsaturated fatty acids, but do not seem to be as beneficial.
Olive oil also contains many phytochemicals such as polyphenols, phytosterols and vitamin E, which are anti-oxidant and anti-inflammatory. The amount depends on the kind of olive oil: extra-virgin is the first oil obtained by mechanically pressing olives, and contains much more phytochemicals than common or virgin olive oil. If the benefits of olive oil are largely due to its phytochemicals, extra-virgin oil should be much better for you than any other variety.
The Predimed (Prevencion con Dieta Mediterranea) is a Spanish study trying to understand which components of the Mediterranean diet are the most important and why. 7216 older adults at high risk of cardiovascular disease participated, and were randomised in three groups. They all continued with their usual Mediterranean diet, but one group added more olive oil, a second group consumed extra nuts, and the third group reduced the amount of fats. In their latest publication, the researchers looked at the effects of olive oil on cardiovascular disease. (I have blogged about the results concerning nuts previously.)
Sure enough, consuming more olive oil was associated with a reduced risk of cardiovascular disease, but the association was due to the use of extra-virgin olive oil: for each 10g/day more extra-virgin olive oil the risk of having cardiovascular disease was reduced by 10%, and the risk of dying from it by 7%. Using common olive oil did not have any benefits.
The researchers could not find a reduced risk of cancer, but they did not examine specific types of cancer. Other studies however, have shown that olive oil reduces the risk of breast cancer and some digestive and respiratory cancers.
M Guasch-Ferre, F B Hu, M A Martinez et al. Olive oil intake and risk of cardiovascular disease and mortality in the PREDIMED study. BMC Medicine. 2014: 12: 78. doi: 10.1186/1741-7015-12-78. Accessed on 20/05/2014.
E Waterman and B Lockwood. Active components and clinical applications of olive oil. Altern Med Rev. 2007; 12(4): 331-342.